How to transfer familiar relationships to a new save?
Yes, you can reestablish familiar relationships in a new save for sims moved from another one. I did it when I created my new save last year and moved around 400 sims from my old save to the new one. You will need MCCC which you can find a link to in this post: [INFORMATION] Common Game Fixing Mods - Hero Approved - Answer HQ (ea.com). Just scroll down to MC Command Center and follow that link. There is a relationship module in that mod that lets you set the relationships and afterwards, it will show correctly in the family tree for the most part. The one thing that it seems to have a problem with is same sex couples and setting 2 mothers or fathers. Those take more work to get them right.
It will take a lot of time and effort on your part to do it. And the bigger the family tree, the more complex it will be. You should start either at the top of the family tree or the bottom if possible and work your way down or up as applicable. Babies can't be added to the family tree until they age up to infants (shouldn't be a problem though if they are still in the household with their parents). For extended relationships, like grandparents, aunts, uncles and cousins, you may need to add relationship bits in addition to setting the direct relationship for things in the family tree to display properly. There will be times where relationships won't seem to hold and you have to do them over or in some cases, undo then reset them again. But in the end, you can get everything to be right.
Hope this helps.
